Widgets won't work right if you have background stuff going at the same time, unless your background stuff is forked or threaded. The execution pointer can only be at one place at a time in a process, and eventloop widgets won't work unless that eventloop is in control. Now there are exceptions to this. If in your while loop, you do DoOneEvent, and also run simple things like increments or file reads, you can keep things responsive. But if you try to run backticks or system on commands, or slow db accesses, it will make the gui unresponsive.

The best thing is to tell us what you are trying to do in the background.

As far as the DoOneEvent being slow, did you run my Tk version? I get very rapid response, where the digits 1 to 10 are repeatedly printed each second.